The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 05, 1995
Filed:
Feb. 25, 1994
Hisashi Kawabata, Tokyo, JP;
NEC Corporation, , JP;
Abstract
A clock recovery circuit having a feedback system in a .pi./4 shift QPSK demodulator, comprising a signal state transition detector for detecting state transitions between consecutive symbols of the demodulated baseband signal which is formed from the detected baseband signal by .pi./4 reverse shifting. According to degree of the detected symbol state transition, the 1/2-symbol delayed baseband signal is shifted by the amount of .pi./8 in phase. According to direction of the detected symbol state transition, the .pi./8 phase shifted baseband signal is converted into an error signal in use for the feedback system. An oscillator generates a clock signal of a frequency controlled by the error signal such that the error signal is reduced in the feedback system.